Base sheet of corrugated cardboard or other stiff sheet material for use in forming various three-dimensional articles, and kit including same

ABSTRACT

A base sheet of stiff material, particularly corrugated cardboard, is cut according to a predetermined configuration, is formed with a predetermined arrangement of fold lines, to enable the sheet to be foldable into a three-dimensional article having a polygonal bottom wall circumscribed by a plurality of erect side walls. One described embodiment is in the form of a kit including such a base sheet cut and formed with fold lines to define a rectangular unit, the kit also including further cardboard sheets to define partitions for the unit. A second embodiment is described wherein the base sheet is cut to define a unit of a modular configuration permitting a plurality of such units to be assembled in a modular fashion to define a shelf or bookcase.

RELATED APPLICATION

This application is related to U.S. application Ser. No. 11/______, concurrently filed with the instant application titled “Kits For Use In Forming Three-Dimensional Articles, Particularly Articles Of Furniture, From Flat Cardboard Sheets”, and assigned to the same assignee as the instant application.

FIELD AND BACKGROUND OF THE INVENTION

The present invention relates to base sheets of stiff sheet material for forming various three-dimensional articles, and also to kits including such base sheets. The invention is particularly useful for forming various three-dimensional articles using corrugated cardboard in a “do it yourself” manner, and is therefore described below with respect to such an application.

Corrugated cardboard sheets have widely been used in constructing inexpensive, light-weight containers, as well as other types of articles in a “do it yourself” manner. Examples of cardboard kits for constructing various articles of furniture, particularly for children, are described in U.S. Pat. Nos. 4,067,615, 4,934,256 and 6,083,580. However, such kits have not yet found widespread use because of the difficulty in designing the base sheets, as well the other elements of the kit, in such form as to permit them to be supplied in a compact flat condition for shipping, handling or storage, and to be folded in a quick and facile manner to form a three-dimensional article which has dimensional stability, structural rigidity and a pleasing appearance.

OBJECTS AND BRIEF SUMMARY OF THE PRESENT INVENTION

An object of the present invention is to provide a base sheet of stiff sheet material, particularly corrugated cardboard, and also a kit including such a base sheet, for use in forming three-dimensional articles having advantages in one or more of the above respects.

According to a broad aspect of the present invention, there is provided a base sheet of stiff sheet material cut according to a predetermined configuration, and including a predetermined arrangement of fold lines to enable the base sheet to be foldable from a flat condition to a three-dimensional condition defining an article having a polygonal bottom wall circumscribed by a plurality of erect side walls; the predetermined arrangement of fold lines including: (a) a plurality of fold lines in the central region of the base sheet to define the bottom wall on the inner side of the fold lines and the side walls on the outer side of the fold lines; and (b) a fold line midway in each side wall to define an outer section of the side wall foldable over an inner section of the side wall; the outer section of each side wall, when folded over the inner section of the respective side wall, including an outer edge engageable with the bottom wall to firmly retain the respective side wall erect in the three-dimensional condition of the article and to expose for view a folded edge, rather than a cut edge, of each side wall.

According to further features in the described preferred embodiment, the base sheet is formed with recesses in the central region inwardly of the fold lines defining the bottom wall; and the outer edge of the outer section of each of the side walls is formed with a projection receivable in the recesses when the outer sections are folded over the inner sections to firmly retain the side walls erect. In addition, the base sheet is cut, and is formed with further fold lines, to define a bendable flap on each of the inner sections of alternative side walls, each flap being insertable between the inner and outer sections of the adjacent side wall, to more firmly retain all the side walls in an erect position in the three-dimensional condition of the article. In addition, the base sheet is

Two embodiments of the invention are described below for purposes of example, in which the three-dimensional article is of rectangular configuration, and the base sheet is of corrugated cardboard.

In one described embodiment, the base sheet is included in a kit which kit also includes a partition, preferably a plurality of partitions, to be applied between two opposed side walls of the three-dimensional article when in is three-dimensional condition. Each partition is defined by another sheet of cardboard bent over itself at a mid-portion thereof to expose for view only the folded edges, and not cut edges, and also to define two parallel sections, each formed with a bendable flap at its opposite ends each receivable between the inner and outer sections of one of the opposed side walls. The outer sections of the two opposed side walls are each formed with a slot for receiving the partition sheet with the flaps of the partition received between the outer and inner sections of the respective side wall.

In another described preferred embodiment, the flaps on the inner sections of the alternate side walls receivable within the inner and outer sections of the adjacent side walls include interengaging ribs and recesses. In addition, the inner sections of the side walls formed with the flaps, and the outer sections of the adjacent side walls, include interengaging ribs and recesses. Such a construction firmly retains the outer sections of all of the side walls in an erect position with respect to the bottom wall in the three-dimensional condition of the article, with the folded over outer sections concealing these interengaging ribs and recesses, thereby presenting a neat appearance.

The latter embodiment is particularly useful as a modular unit, for assembly with a plurality of like modular units in the form of a wall-mounted or floor-mounted shelving or bookcase.

As will be described more particularly below, base sheets constructed in accordance with the foregoing features of the invention may be produced in volume and at low cost, may be packaged and shipped in a compact flat condition, and may be used for assembling in a “do it yourself” manner, a wide variety of three-dimensional articles, particularly open cabinets, partitioned containers, bookcases, shelving and the like, having a high degree of dimensional stability and structural rigidity, and also presenting a very pleasing appearance.

Further features and advantages of the invention will be apparent from the description below.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is herein described, by way of example only, with reference to the accompanying drawings, wherein:

FIG. 1 illustrates one form of three-dimensional article, such as an open cabinet, partitioned container or the like, that may be formed from a flat base sheet or kit constructed in accordance with the present invention;

FIG. 2 illustrates a kit including the basic components, in flat sheet form as supplied by the factory and as to be used by the user, for assembling the three-dimensional article of FIG. 1;

FIG. 3 more particularly illustrates the various sheets, in flat form, used in making the components of the kit in FIG. 2;

FIG. 4 illustrates the partition sheets in folded form in the kit of FIG. 2;

FIG. 5 is a top plan view illustrating the base sheet in the kit of FIG. 2;

FIG. 6 is a bottom plan view of the base sheet in the kit of FIG. 2;

FIG. 7 illustrates the components of the kit of FIG. 2 in an intermediate stage of assembly of the three-dimensional article;

FIGS. 8 a-8 i illustrate the sequential steps used in forming, from the components of the kit of FIG. 2, the three-dimensional article of FIG. 1;

FIG. 9 illustrates another three-dimensional article which may be formed from a flat base sheet constructed in accordance with the present invention;

FIG. 10 illustrates the base sheet in flat form, as produced by the factory and as to be used by the user, for producing the three-dimensional article illustrated in FIG. 9;

FIG. 11 illustrates, in flat form, the various sheet components used in making the base sheet of FIG. 10;

FIGS. 12 and 13 illustrate top and bottom faces of the base sheet of FIG. 10;

FIGS. 14 a-14 d illustrate the sequence of operations involved in using the base sheet of FIG. 10 for forming the article of FIG. 9;

FIGS. 15 a, 15 b and 15 c illustrate how the article of FIG. 9 can be constructed to serve as a modular unit for assembling various configurations of shelving, bookcases, and the like;

FIGS. 16 a, 16 b., 17 a, 17 b and 18 a, 18 b illustrate other variations in the modular units of FIGS. 15 a and 15 b;

FIG. 19 illustrates a further variation in the modular unit;

and FIGS. 20 and 21 illustrate examples of various configurations of shelving, bookcases, and the like that can be assembled with the modular units of FIGS. 9-21.

It is to be understood that the foregoing drawings, and the description below, are provided primarily for purposes of facilitating understanding the conceptual aspects of the invention and possible embodiments thereof, including what is presently considered to be a preferred embodiment. In the interest of clarity and brevity, no attempt is made to provide more details than necessary to enable one skilled in the art, using routine skill and design, to understand and practice the described invention. It is to be further understood that the embodiments described are for purposes of example only, and that the invention is capable of being embodied in other forms and applications than described herein.

DESCRIPTION OF PREFERRED EMBODIMENTS

As indicated earlier, the invention provides a base sheet, or a kit including such a base sheet, which is cut according to a predetermined configuration and includes a predetermined arrangement of fold lines, to enable the base sheet to be folded in a particular three-dimensional article. The base sheet may thus be supplied alone, or as a component of a kit. It can be produced, shipped and stored in a compact flat condition, and then used by the purchaser to form, in a quick and facile manner, three-dimensional articles having high dimensional rigidity and structural stability, and also a pleasing appearance.

Two embodiments of the invention are described below for purposes of example.

The Embodiment of FIGS. 1-8 i

FIGS. 1-8 i illustrate the invention embodied in a base sheet, and also in a kit including such a base sheet, to be used for producing a cabinet, partitioned receptacle, or the like, as illustrated in FIG. 1. The two basic components of the kit are illustrated in flat form in FIG. 2. FIGS. 3-6 illustrate the construction of these basic components; and FIGS. 7, and 8 a-8 i illustrate the manner of using those components for producing the article of FIG. 1.

The three-dimensional article illustrated in FIG. 1, therein generally designated 100, is a cabinet, partitioned receptacle or the like, of rectangular configuration. It includes four side walls 101, 102, 103, 104; a bottom wall 105; a plurality of transverse partitions 106 of one construction, and end partitions 107 of a slightly different construction; and a longitudinal partition 108.

FIG. 2 illustrates the contents of the kit, in flat form as supplied to the user from the factory, which may be used for assembling the three-dimensional article of FIG. 1. Thus, as shown in FIG. 2, such a kit includes a base sheet 110 cut according to a predetermined configuration and formed with a predetermined arrangement of fold lines as will be described more particularly below. The kit also includes a plurality of partitions 106 and 107 also supplied in flat form. FIG. 3 more particularly illustrates the contents of the kit in flat sheet form as initially produced at the factory, whereas FIGS. 4-6 illustrate these components in the folded form and adhesively joined form as supplied by the factory to the purchaser.

As shown in FIG. 3, each of the transverse partitions 106 and 107 is made of a flat corrugated cardboard sheet of the configuration illustrated, each formed with a fold line 106 a, 107 a, extending midway for its full length to divide the respective sheet into two sections on opposite sides of the fold line. One section is coated with an adhesive, as shown (by dotted lines) at 106 b, 107 b, to enable it to be folded against, and adhesively joined to, the other section. In the case of the end transverse partitions 107, the adhesively-coated section of the partition is of slightly shorter length than the other section, so as to produce a single bendable flap 107 c in each of these partitions. In the case of the middle transverse partitions 106, the two sections are of equal length, but the adhesive coating on one section is applied only to the central section of the respective partition, leaving both opposite end portions uncoated, so that in the folded condition of these partitions, two such flaps 106 c are formed at the non-adhesively-joined ends of the partition.

As further seen in FIG. 3, the flap at one end of each partition is formed with a projection, as shown at 106 d, 107 d, whereas the opposite end of the respective partition is formed with a recess, as shown at 106 e, 107 e. As will be described more particularly below and as shown particularly in FIG. 7, the flaps at the ends of these partitions, with the ribs and recesses of adjacent partitions interengaging, are used for mounting the partitions within the article in a manner to provide dimensional rigidity, structural stability, and a very pleasing appearance.

Each partition is further formed with a slot, 106 f, 107 f, for accommodating the longitudinal partition 108.

The longitudinal partition 108 (FIG. 1) is not defined by a separate cardboard sheet, but rather is integrally constructed with the bottom wall 105 of base sheet 110, as will be described more particularly below.

The construction of the base sheet 110 is also illustrated in FIG. 3. It is constructed of a plurality of flat cardboard sheets 111-118 each cut as shown in FIG. 3. Each is formed with slots as shown in full lines in FIG. 3, and is coated with adhesive surfaces as shown in dotted lines in FIG. 3. The arrangement is such that they can all be joined at their adhesively-coated surfaces to produce the base sheet 110 of FIG. 2 to be used to produce the three-dimensional article 100 of FIG. 1. The joining of the sheets 111-118 would in most cases be performed by adhesive at the factory to produce the base sheet 110 to be supplied to the purchaser, but it is contemplated that, in some cases, the actual joining of the various sheets could be done by the purchaser by using an adhesive, or mechanical-type connectors, as will be described below.

Cardboard sheet 111 is of rectangular configuration and serves as the bottom wall 105 of article 100. Sheets 112-115 are adhesively joined at their inner edges 112 a-115 a, to the under surface of sheet 111. They are formed with fold lines 112 b-115 b, to permit these sheets to be bent upwardly to an erect condition with respect to the bottom sheet. Each of the sheets 112-115 is formed with a further fold line, e.g., 112 c midway of its length to permit the sheet to be folded into an inner section, e.g., 112 d, and an outer section, e.g., 112 e.

The two cardboard sheets 112, 113 which, as indicated earlier, constitute the longitudinal sides 102 and 103 of article 100, are formed, in their outer sections, with three equally-spaced slots, e.g., 112 f, for accommodating the three intermediate transverse partitions 107; whereas the outer sections of sheets 114, 115, which define the transverse side walls of article 100, are provided with a single middle slot, e.g., 114 f, to accommodate the longitudinal partition 108.

As further seen in FIG. 3, the outer edges of the two sheets 112, 113, defining the longitudinal side walls 102, 103 of the assembled article 100, are formed with projections, e.g., 112 g, one between each pair of slots formed in the outer section of the respective sheet. As will be described below, these projections are engageable with recesses formed in the bottom wall 105 of the three-dimensional article to firmly secure the side walls in erect condition.

In addition, the inner section of each sheet 112, 113, is formed on each of its opposite ends with an extension, e.g., 112 h, separated by a fold line, e.g., 112 i, defining bendable flaps. As will be described below, these flaps are insertable between the inner and outer sections of the adjacent side walls (namely those defined by sheets 114, 115) to more firmly secure all the side walls in an erect position in the three-dimensional condition of article 100.

The two sheets 114, 115 defining the transverse side walls 104, 105 of article 100, are each formed, in their outer sections, with a single slot 114 f, 115 f, and with two projections 114 g, 115 g on each side of respective slot also engageable with recesses in the bottom wall. In addition, the inner sections of the two sheets 114, 115 are also formed with end flaps 114 i, 115 i; these are adhesively coated so as to enable them to be folded against, and adhesively joined, to the inner surfaces of the respective side wall sections for reinforcement purposes.

The two further cardboard sheets 116, 117 illustrated in FIG. 3 are adhesively coated, as shown by the dotted lines, and are of a configuration to be adhesively joined to the inner surfaces of the inner sections of sheets 112, 113 serving as the longitudinal side walls 102, 103 of article 100. Sheets 116, 117 serve to reinforce these longitudinal side walls and therefore are preferably also are of corrugated cardboard, with the corrugations running perpendicularly to those in sheets 112, 113.

Sheet 118 illustrated in FIG. 3 is the upper sheet of the bottom wall 105 in the three-dimensional article 100 illustrated in FIG. 1. It is formed with a central fold line 118 a to permit the sheet to be folded into two sections and secured to bottom wall sheet 118 by an adhesive 118 b; sheet 118 is formed with recesses 118 c on its outer edges for receiving projections 112 g-115 g of the side wall sheets 112-115. Sheet 118 is further formed with bendable flaps 118 d at its opposite ends, to be received between the two sections of each of the transverse end walls of sheets 114, 115.

It will be seen that when sheet 118 is folded along its fold lines and adhesively joined at its outer sections 118 b to sheet 111, the middle sections 118 e are forced to an erect position in folded relation to each other to constitute the longitudinal partition 108, with the folded edge along fold lines 118 a exposed for view (rather than a cut edge), and with the slots 108 f for receiving the transverse partitions 106.

FIG. 4 illustrates the folded and adhesively-joined condition of the partitions 106-108. FIG. 5 is a top view of the base sheet 110 in its flat condition when constructed as described above, and FIG. 6 is a bottom view of base sheet 110. FIG. 7 illustrates the base sheet 110 in its substantially flat condition except that sheet 118 is in its folded condition about fold lines 118 a to define the longitudinal partition 108, and with the other partitions 106 and 107 in proper position to show how these partitions cooperate with each other and the various elements of the base sheet.

FIGS. 8 a-8 i illustrate the sequence of operations involved in assembling the three-dimensional article 100 illustrated in FIG. 1 from the base sheet 110 and the partitions 106 and 107. As described above, the article, when so assembled, has a high degree of dimensional rigidity and structural stability, and also presents a pleasing appearance, particularly since all edges of the article are defined by fold lines, and not by cut edges. The surfaces of the various sheets involved to appear as outer surfaces in the three-dimensional article 100 may be colored or otherwise ornamented to enhance the aesthetic appeal of the assembled article.

The Embodiment of FIGS. 9-21

FIGS. 9-21 illustrate the invention embodied in a construction for producing a square-shaped three-dimensional article, generally designated 200 in FIG. 9. Such an article may be used as a simple container or storage device, or as a modular unit for assembly, with other like modular units, into wall-mounted or floor-mounted shelving, bookcase, cabinet, and the like.

The three-dimensional article 200 illustrated in FIG. 9 includes a square bottom wall 201, and four side walls 202-205 to be folded into an erect position around the bottom wall 201. Article 200 is made of corrugated cardboard, and is constituted of a single base sheet 210 illustrated in FIG. 10. As described below, base sheet 110 is constructed of a plurality of cardboard sheets each cut according to a predetermined configuration, and joined together at selected surfaces. Base sheet 110 includes a predetermined arrangement of fold lines, to enable the sheet also to be supplied in flat form and to be formed into a three-dimensional article, e.g., article 200 illustrated in FIG. 9, having a high degree of dimensional stability and structural rigidity, as well as exposing only fold lines, rather than cut edges, to present a pleasing appearance.

As shown in FIG. 10, base sheet 210 includes a central section 211 serving as the bottom wall 201 of article 200, and four sections 212-215 serving as the side walls 202-205 of the article. Base sheet 210 is constructed of several cardboard sheets, as more particularly illustrated in FIGS. 11-13, joined together at selective adhesively-coated surfaces to enable the base sheet, by simple folding operations, to be formed into the three-dimensional article 200 illustrated in FIG. 9.

Thus, as shown in FIG. 11, base sheet 210 is constituted of a central sheet 221 defining the bottom 201 of article 200, and four additional sheets 222-225, defining the four side walls 202-205 of article 200. In this case, the three-dimensional article 200 so produced is of a modular construction, as illustrated in FIGS. 15 a and 15 b, permitting a plurality of similar units to be assembled in a modular manner, as illustrated in FIG. 15 c and also in FIGS. 20 and 21. For this reason, the central sheet 221 is of square configuration but includes a cut-out 221 a at one corner to provide the modular feature, as will be described below.

Base sheet 210 includes a further top sheet 226 which is adhesively joined over the upper surface of the central sheet 221. Top sheet 226 is similarly formed with a cut-out 226 a in one corner to be in alignment with cut-out 221 a of the central sheet 221 when sheet 226 is adhesively joined to sheet 221. The corrugations in sheet 226 are perpendicular to those in sheet 221 for strengthening purposes. In addition, the outer edges of the top sheet 226 are formed with recesses 226 b, to serve as recesses in the outer edges of the central sheet 221 when joined thereto. These recesses are cooperable with projections in sheets 222-225 when the latter sheets are folded to an erect position to define the side walls 202-205 of article 200, as will be described more particularly below.

Base sheet 210 includes two further cardboard sheets 227, 228, adhesively joined to the inner surfaces of the outer sections of opposed sheets 224, 225 for strengthening purposes. Sheets 227, 228 may therefore also be of corrugated cardboard, but with the corrugations running perpendicularly to the corrugations in the outer sections of sheets 224, 225.

Base sheet 210 includes further strengthening strips 229 applied to the inner surfaces of the outer edges of the outer two opposed sheets 222, 223, for strengthening those edges. Strengthening strips 229 may therefore also be of corrugated cardboard, with the corrugations running perpendicularly to those in their respective sheets 222, 223.

The two sheets 222, 223, defining the two opposed side walls 202, 203 of the three-dimensional article 200, are of the same construction except for a slight modification in sheet 223 to provide the modular feature. Similarly, the two sheets 224, 225, defining the other opposed side walls of the three-dimensional article 200, are also of basically the same construction, except for a slight modification in sheet 224 to provide the modular feature.

As seen in FIG. 11, the four sheets 222-225 include adhesively-coated portions 222 a-225 a, along their inner edges for adhesively joining to the outer edges of the central sheet 221. In addition, the four sheets 222-225 include mid-fold lines 222 b-225 b dividing the respective side wall into an inner section 222 c-225 c and an outer section 222 d-225 d, foldable over the inner section. The edge of each outer section 222 d and 223 d is further formed with projections 222 e and 223 e, whereas the outer edges of sheets 227 joined to the outer sections 224 d and 225 d of sheets 224 and 225, are also formed with projections 224 d and 225 d. These projections are engageable with the recesses 226 b defined by the upper sheet 226 when bonded to the lower bottom sheet 221 to firmly support the side walls in an erect position.

Sheet 222 defining side wall 202 is further formed with a hook formation 222 f at each of the opposite ends of its outer section 222 d. Sheet 222 is further formed with a flap 222 g at each of the opposite ends of its inner section 222 c. Flaps 222 g are to be folded over the inner face of the inner section 222 c of the respective sheet and adhesively joined thereto for strengthening purposes.

The opposed sheets 223 defining the opposite side wall 203 of article 200 is similarly constructed as described above with respect to sheet 222, except that it is formed with slots 223 h-223 j to provide the modular feature in article 200.

The two sheets 224, 225, defining the other pair of opposed side walls 204, 205 of article 200, are similarly constructed. Besides their adhesively coated inner sections (e.g., 224 a) and mid-fold lines (e.g., 224 b), the outer edges of the outer sections are similarly formed with projections (e.g., 224 e) cooperable with recesses 226 b in the bottom wall when sheets 224 and 225 are folded over to define the side wall 204 and 205 of the article.

The inner sections of the two sheets 224 and 225 are further formed with bendable flaps, e.g., 224 f, at their opposite ends, but in this case one flap is formed with a recess, e.g., 224 g, while the other is formed with a complimentary projection, e.g., 224 h. As shown in FIG. 11, sheet 225 at the opposite side of article 200 is constructed in the same manner as sheet 224, except that sheet 224 is provided with various slots 224 i, 224 j, 224 k, to accommodate the modular feature.

FIG. 12 illustrates the inner face of the base sheet 210 when constructed as described above, and FIG. 13 illustrates the outer surface of the base sheet.

FIGS. 14 a-14 d illustrate the sequence of folding operations for folding the base sheet into the three-dimensional article 200 illustrated in FIGS. 15 a and 15 d.

It will be seen that the only operations required are folding operations, and that a high degree of dimensional stability and structural rigidity is effected by the engagement of projections 222 e-225 e into the recesses 226 b in the bottom wall of the article, by the engagement of the hook projections corresponding to 222 f into the recesses corresponding to 224 g, and by the engagement of projections corresponding to 224 h in the recesses 224 f. It will also be seen that the all the interengaging projections are concealed by the folded over outer sections of each of the sheets 222-225; and that only fold lines, and no cut edges, are exposed for view. The so-produced three-dimensional article thereby presents an extremely pleasing appearance, which may be enhanced by coloring, or otherwise ornamenting, all surfaces exposed for view.

It will also be appreciated that the article produced, when including the cut-out 221 a in the bottom wall 221, together with the other slots in the side walls cooperable therewith as described above, enables a plurality of such units to be assembled in modular fashion. FIGS. 15 a-19 illustrate various constructions, designated 200 a-200 d, respectively, that can be provided for the modular construction; and FIGS. 20 and 21 illustrate various modular configurations that can be assembled using a plurality of units 200.

The invention has been described above with respect to several preferred embodiments for purposes of example only, it will be appreciated that many variations, modifications and other applications of the invention may be made. For example, while various surfaces are described as being joined by adhesive at the factory, such surfaces could be merely marked for joining with adhesive applied by the purchaser. Also, such surfaces could be merely coated with a moisture-responsive adhesive such that the purchaser would moisten the respective surfaces and effect the joining. In addition, other methods of joining could be used, for example buttons formed on one surface snappable into sockets formed in the other surface to be joined, or by mechanical “hook and loop” type fasteners (e.g. “Velcro”).

In addition, while the invention has been described with respect to using cardboard sheets, the invention could also be applied to other materials, such as thin plastic sheets. Further, while the invention has been described with respect to furniture articles, other types of articles could be assembled, such as receptacles, toys, etc.

Many other variations, modifications and applications of the invention will be apparent. 

1. A base sheet of stiff sheet material cut according to a predetermined configuration and including a predetermined arrangement of fold lines to enable the base sheet to be foldable from a flat condition to a three-dimensional condition defining an article having a polygonal bottom wall circumscribed by a plurality of erect side walls; said predetermined arrangement of fold lines including: (a) a plurality of fold lines in the central region of the base sheet to define said bottom wall on the inner side of the fold lines and said side walls on the outer side of said fold lines; and (b) a fold line midway in each side wall to define an outer section of the side wall foldable over an inner section of the side wall; said outer section of each side wall, when folded over the inner section of the respective side wall, including an outer edge engageable with said bottom wall to firmly retain the respective side wall erect in the three-dimensional condition of the article and to expose for view a folded edge, rather than a cut edge, of each side wall.
 2. The base sheet according to claim 1, wherein: said base sheet is formed with recesses in said central region inwardly of the fold lines defining said bottom wall; and the outer edge of the outer section of each of said side walls is formed with a projection receivable in said recesses when said outer sections are folded over said inner sections to firmly retain said side walls erect.
 3. The base sheet according to claim 1, wherein said base sheet is cut, and is formed with further fold lines, to define a bendable flap on each of the inner sections of alternate side walls, each flap being insertable between the inner and outer sections of the adjacent side wall to more firmly retain all said side walls in an erect position in the three-dimensional condition of the article.
 4. The base sheet according to claim 3, wherein said three-dimensional article is of rectangular configuration.
 5. The base sheet according to claim 4, wherein the base sheet is of corrugated cardboard.
 6. A kit including the base sheet according to claim 5, and at least one partition to be applied between two opposed side walls of the three-dimensional article when in its three-dimensional condition; said partition being defined by another sheet of cardboard bent over itself at a mid-portion thereof to expose for view only the folded edge, and not a cut edge, and also to define two parallel sections, each formed with a bendable flap at its opposite ends each receivable between the inner and outer sections of one of said opposed side walls; the outer section of said two opposed side walls being each formed with a slot for receiving said partition sheet with the flaps of the partition received between the outer and inner sections of the respective side wall.
 7. The kit according to claim 6, wherein said kit includes a plurality of said partitions to be applied to said opposed side walls in parallel spaced relationship to each other; and the outer section of each of said opposed side walls is formed with a said slot for receiving one of said partitions.
 8. The kit according to claim 6, wherein said kit further includes a further partition between two other opposed side walls; said further partition being defined by yet another sheet of cardboard joined to said bottom wall and bent over itself at a mid-portion thereof to expose for view only the folded edge, and not a cut edge, and to define two parallel sections each formed with a bendable flap on its opposite ends each receivable between the inner and outer sections of one of said opposed side walls; said further partition further including a slot for accommodating said first-mentioned partition.
 9. The kit according to claim 6, wherein said base cardboard sheet is reinforced by additional corrugated cardboard sheets joined to the portions of said base corrugated cardboard sheet defining said bottom wall and the inner sections of at least two opposed side walls; the corrugations of said additional cardboard sheets extending perpendicularly to the corrugations of said base cardboard sheet.
 10. The kit according to claim 6, wherein all edges of said base cardboard sheet and all said partitions exposed for view in the three-dimensional condition of said article are fold lines of said base cardboard sheet and said partitions.
 11. The base sheet according to claim 3, wherein said flaps on the inner sections of said alternate side walls receivable within the inner and outer sections of said adjacent side walls include interengaging ribs and recesses.
 12. The base sheet according to claim 11, wherein the inner sections of said side walls formed with said flaps, and the outer sections of said adjacent side walls, include interengaging ribs and recesses for firmly retaining the outer sections of all of said side walls in an erect position with respect to said bottom wall in the three-dimensional condition of the article.
 13. The base sheet according to claim 12, wherein said central region defining said bottom wall is formed with a rectangular cut-out at a corner thereof, and wherein the respective side walls and flaps at the opposite corners of said rectangular cut-out are formed with slots, to permit a plurality of said three-dimensional articles to be assembled together in a modular fashion.
 14. A kit comprising a cardboard base sheet cut according to a predetermined configuration, and including a predetermined arrangement of fold lines to enable the cardboard base sheet to be foldable from a flat condition to a three-dimensional condition defining an article having a rectangular bottom wall and four erect side walls; said predetermined arrangement of fold lines including: (a) a plurality of fold lines in the central region of the cardboard sheet to define said bottom wall on the inner side of the fold lines and said side walls on the outer side of said fold lines; and (b) a fold line midway in each side wall to define an outer section of the side wall foldable over an inner section of the side wall; said outer section of each side wall, when folded over the inner section of the respective side wall, including an outer edge engageable with said bottom wall to firmly retain the respective side wall erect in the three-dimensional condition of the article and to expose for view a folded edge, rather than a cut edge, of each side wall; said kit further comprising at least one partition to be applied between two opposed side walls of the three-dimensional article when in its three-dimensional condition; said partition being defined by another sheet of cardboard bent over itself at a mid-portion thereof to expose for view only the folded edge, rather than a cut edge, and to define two parallel sections, each formed with a bendable flap at its opposite ends; the outer section of said two opposed side walls being each formed with a slot for receiving said partition sheet with the flaps of the partition received between the outer and inner sections of the respective side wall.
 15. The kit according to claim 14, wherein: said cardboard base sheet is formed with recesses in said central region inwardly of the fold lines defining said bottom wall; and the outer edge of the outer section of each of said side walls is formed with a projection receivable in said recesses when said outer sections are folded over said inner sections to firmly retain said side walls erect.
 16. The kit according to claim 15, wherein said cardboard base sheet is cut, and is formed with further fold lines, to define a bendable flap on the inner section of alternate side walls, each flap being insertable between the inner and outer sections of the adjacent side wall to more firmly retain all said side walls in an erect position in the three-dimensional condition of the article.
 17. A sheet of corrugated cardboard cut according to a predetermined configuration, and including a predetermined arrangement of fold lines to enable the cardboard sheet to be foldable from a flat condition to a three-dimensional condition defining an article having a polygonal bottom wall circumscribed by a plurality of erect side walls; said predetermined arrangement of fold lines including: (a) a plurality of fold lines in the central region of the cardboard sheet to define said bottom wall on the inner side of the fold lines and said side walls on the outer side of said fold lines; and (b) a fold line midway in each side wall to define an outer section of the side wall foldable over an inner section of the side wall; said outer section of each side wall, when folded over the inner section of the respective side wall, including an outer edge engageable with said bottom wall to firmly retain said side walls erect in the three-dimensional condition of the article; said base sheet being cut, and being formed with further fold lines, to define a bendable flap on each of the outer sections of alternative side walls each insertable between the inner and outer sections of the adjacent side walls; the outer sections of said side walls having said flaps, and the inner sections of said adjacent side walls, including interengaging ribs and recesses for firmly retaining the outer sections of all of said side walls in an erect position with respect to said bottom wall in the three-dimensional condition of the article.
 18. The cardboard sheet of claim 17, wherein: said cardboard sheet is formed with recesses in said central region inwardly of the fold lines defining said bottom wall; and the outer edge of the outer section of each of said side walls is formed with a projection receivable in said recesses when said outer sections are folded over said inner sections to firmly retain said side walls erect.
 19. The cardboard sheet according to claim 18, wherein said base sheet is cut, and is formed with further fold lines, to define a bendable flap on alternate side walls insertable between the inner and outer sections of the adjacent side walls, to more firmly secure all said side walls in an erect position in the three-dimensional condition of the article.
 20. The cardboard sheet according to claim 19, wherein said central region defining said bottom is formed with a rectangular cut-out at a corner thereof, and wherein the respective side walls and flaps at the opposite corners of said rectangular cut-out are formed with slots, to permit a plurality of said three-dimensional articles to be assembled together in a modular fashion. 